Magcard payment is used more and more widely, and POS machines are used more and more. The use of a POS machine directly relates to personal private account information of users. At the same time, when a POS machine is used, private information, such as a password, generally needs to be input by means of a keyboard. When a keyboard is used, a hand of a user generally extends from a side of the keyboard to the keyboard and then presses buttons of the keyboard to input information. This may results in gaps existing between side edges of the hand and other three side edges of the keyboard, and the information input by the user is prone to be peeped through these gaps. Therefore, in order to improve the security of keyboard input, a casing of a POS machine is often provided thereon with a peep-proof cover, which is configured to cover the other three side edges of the keyboard and thereby prevent users from being peeped when they are inputting information. However, a conventional peep-proof cover usually directly covers a casing of a POS machine; when the POS machine is used, the peep-poof cover may be often hit or shook, and it is prone to lead to falling of the peep-proof cover. A POS machine of which a peep-proof cover has fallen off is easy to be peeped when a user inputs information into the POS machine, and this may result in that the user information is stolen.